Device for the magnetic arresting of a switch wheel of a timekeeping device

ABSTRACT

A magnet arresting device for a clock or watch movement including a magnet core housed in a field confining shroud means of magnetically permeable material.

I United States Patent 1151 3,673,792

Scholz 1 1 July 4, 1972 [54] DEVICE FOR THE MAGNETIC ARRESTING OF A SWITCH WHEEL 0F 5 References Cited A TIMEKEEPING DEVICE UNITED STATES PATENTS [721 Schramberg, Germany 3,183,426 5/1965 Haydon ..58/116 M x [73] Assignee: Gebruder Junghans G.m.b.H., Schram- 3,396,531 8/1958 nge et wberg, Germany 3,505,805 4/1970 Cohen et a1 ..58/116 R [22] Filed: March 1971 Primary ExaminerRichard B. Wilkinson 2 122 942 Assistant ExaminerEdith C. Simmons Att0rney-Bums, Doane, Swecker & Mathis [30] Foreign Application Priority Data 57 ABSTRACT March 17, Germany V A magnet arresting device for a clock or watch movement in. cluding a magnet core housed in a field confining shroud U-S- Cl. D, means of magneticany ermeable mate iaL [51] Int. Cl ..G04c 3/04 [58] Field of Search ..5 8/28 D, 116, 116 M; 74/15 8 Claims, 3 Drawing Figures P'ATENTEDJUL 41972 3,573,792

INVENTOR GUNTHER SCHOLZ BY BM, 'L

ATTORNEYS DEVICE FOR THE MAGNETIC ARRESTING OF A SWITCH WHEEL OF A TIMEKEEPING DEVICE RELATED APPLICATION This application discloses an improvement of a timepiece mechanism described in my prior application Ser. No. 875,646, filed Nov. 12, 1969 now US. Pat. No. 3,581,134. The entire disclosure of this prior application is herein incorporated by reference insofar as it relates to or corresponds to illustrated or described aspects of the present invention.

GENERAL BACKGROUND, OBJECTS, AND SUMMARY OF INVENTION The invention relates to a device for the magnetic arresting of a switch wheel of a timekeeping device.

A permanent magnet arrangement has been provided which acts upon the teeth of a switch means, or on a part in engagement with the switch means, and arrests the switch means between consecutive continuous processes.

In the case of a timepiece, for example, a balance clock which is driven electromagnetically without contact, the switch wheel is driven step-by-step by a movement regulating oscillator. In this timepiece, the switch wheel must be held firmly between the individual continuous advancing steps. This firm holding or arresting can be accomplished for example in a magnetic way.

A timepiece has been known where the switch wheel consists of ferromagnetic material and where a permanent magnet bar, magnetized in an axial direction and pointed toward the teeth of the switch wheel, has been arranged on a bed plate.

it has also been known that, instead of acting on the switch wheel, an arresting means may act upon the armature fork. Thus, it has been known for example to use a fork made of ferromagnetic material which has two prongs separated from one another by a nonmagnetic part, for example an air gap. Each prong, in each end position of the fork, faces a bar-shaped, fixed permanent magnet.

In the case of these partially nonmagnetic arresting arrangements, the permanent magnet produces a large stray field, which exerts an unfavorable influence on the isochronism behavior of the movement regulator. As a result of this, small irregular jumps in the movement may occur.

Arresting arrangements of the initially mentioned type have already been known, where a magnetic field return element has been arranged on the switch means restraining permanent magnet, which return element closes the magnetic circuit as far as possible. These known arrangements however have relatively large dimensions so that they cannot be used in many cases, especially in the case of small watches, such as wrist watches.

The object of the invention is the production of an arrangement of the initially mentioned type, which can be produced with very small dimensions and nevertheless will assure a safe arresting.

According to the invention this will be achieved through the fact that the permanent magnet arrangement consists of a barshaped permanent magnet and a pot-like return clement encircling the permanent magnet. A stop magnet devised in such a way can be produced with extraordinarily small dimensions. At the same time, the straying is kept at a minimum. A permanent magnet arrangement developed in such a way can be housed practically in every watch case.

The pennanent magnet arrangement preferably is axially shiftable for the purpose of adjusting the holding force in the direction of the part cooperating with it. But it is also possible to mount the bar-like permanent magnet so that it is axially shiftable in relation to the pot-shaped return element, whereby, for example, the pot-shaped return element may be fixedly mounted. In this way, it is possible in a simple manner to adjust the holding force of the magnet within wide limits. Of course, a combination of these mountings may be employed to provide greater control over the axial and lateral extent of field stray.

LII

The permanent magnet may, for example, consist of a platinum-cobalt alloy.

In order to further decrease the influence of the stop magnet on the moved parts, the part cooperating with the permanent magnet arrangement may consist of nonmagnetic body material coated with a layer consisting of ferromagnetic material with high permeability.

DRAWINGS The invention is explained in more detail in the following paragraphs on the basis of the drawings, and two embodiments presented by way of examples.

In the Drawings: 2

FIG. 1 shows in plan view the stop arrangement according to the invention in which a stop magnet acts upon a switch armature fork;

FIG. 2 shows a side view of the arrangement according to FIG. 1, partly in section; and

FIG. 3 shows a stop arrangement according to the invention in which a stop magnet acts directly on the teeth of a switch wheel.

DETAILED DESCRIPTION In FIG. 1 a switch or armature fork has been designated by 10. Pork 10 has been swivelably mounted in a bed plate 11 Y with the help of an axle 16. The swiveling movement of switch fork 10 is limited by stops l4 and 15.

A slit 13 has been provided in the part 10c of the switch fork, with which a peg engages. This peg would be arranged on a movement regulating oscillator, for example, a balance, and would move the fork 10 alternatingiy into one of the two end positions as determined by stop means 14 and 15.

At places 10a and 10b, pallets 17 and 18 have been inserted, which cooperate with switch wheel 19. The switch wheel 19 is mounted on a shaft 21 which carries a pinion, which has not been shown and which engages with the drive mechanism of the hands. A look wheel 20, connected with wheel 19, can be provided additionally on the shaft 21. A lock spring 22 has been provided with a jewel 23 engaging with teeth of the periphery of lock wheel 20 so as to provide a type of ratchet control in relation to the rotation of means 12-20.

In the case of the embodiment shown by way of example, the arresting or restraining of the switch fork 10 in its end position is achieved with the aid of a permanent magnet arrangement 24/25. This arrangement acts upon the two prongs 10d and 10e, i.e., in each of the end positions of the fork v10, on one of the above mentioned prongs. In the end position shown in FIG. I, the permanent magnet arrangement 24/25 acts upon the prong l0e.

In order to make possible an action of the permanent magnet arrangement 24/25 on the prongs 10d and 10s of the switch fork, the switch fork 10 may consist of a ferromagnetic material. Effectively, however, the body of switch fork 10 may consist of a nonmagnetic material, such as for example beryllium, and the switch fork 10 in the area of the permanent magnet arrangement 24/25 may be coated with a covering 26 of ferromagnetic raw material with high permeability.

As can be seen in FIG. 1, the prongs 10d and We are separated by an air gap 12.

The permanent magnet arrangement, as can best be seen in FIG. 2, consists of a bar-like permanent magnet 24, which is magnetized in an axial direction, and a pot-shaped return element or shroud means 25 made of ferromagnetic raw material of high permeability. The permanent magnet bar 24 may consist for example of a platinum-cobalt alloy.

As shown in FIG. 2, the end 25a of pot 25 is disposed in engaged or contiguous relation with one pole end of magnet 24. The other pot end 25b, and over half of the annular body of pot 25 extending upwardly therefrom, is spaced outwardly from the body of magnet 24 by a non-magnetic gap 250 which may comprise an air gap. This gap insures the desired axial intensity of the magnetic field extending from the magnetic into movement restraining cooperation with fork portions 100 or 10d.

A largely closed magnetic circuit is created by the return element 25 completely encircling the permanent magnet 24, and the coating 26 of ferromagnetic material arranged on the switch fork 10, as a result of which a stray field has been largely avoided.

The permanent magnet arrangement 24/25 has extraordinarily small dimensions, so that it can be housed practically anywhere. The arrangement 24/25 may be shifted, for example, in toto in an axial direction in the direction of the part cooperating with it, in order to adjust the holding force. Naturally it is also possible to shift the permanent magnet 24 relative to the return element 25 in order to adjust the holding force in this manner. As a result of that, an adjustment within wide limits is made possible.

In the case of the embodiment according to FIG. 3 given by way of example, numeral 30 designates the body of the balance, which has been arranged on the axle 31, and has been mounted between two bed plates in the customary manner. Balance '30 can contain, for example, a permanent magnet which cooperates with coils, not shown in the drawing. On the balance 30, an angular switch spring 32 has been attached which continues to switch, by one tooth, the switch wheel 33 upon every oscillation of the balance.

The switch wheel 33 consists of a ferromagnetic material with high permeability. The teeth 33a of the switch wheel are engaged by the switch spring 32. The switch wheel has been mounted on an axle 34, which carries a pinion not shown. This pinion engages with the driving mechanism for the hands, likewise not shown.

A permanent magnet arrangement 34/35 has been arranged on a bed plate 36 and acts upon the teeth 33a of the switch wheel 33 and to incrementally restrain or stop the switch wheel. The permanent magnet arrangement 34/35 has been built in the same way as the permanent magnet arrangement according to FIGS. 1 and 2, and therefore it does not need to be described here in more detail.

Naturally, it is possible in this case, too, to make the switch wheel 33 of a nonmagnetic material and to provide sections made of ferromagnetic material on the switch wheel teeth 33a on the side of the switch wheel 33 opposite the permanent magnet arrangement 34/35.

SUMMARY OF ADVANTAGES AND SCOPE INVENTION A major advantage of the invention resides in the provision of a uniquely small magnetic restraining device in a time piece which generates an effectively directed and intensified magnetic restraining field.

A further advantage resides in the use of a pot-like shroud means which facilitates axial adjustment of the shroud means and/or magnet so as to adjust the magnetic field.

In describing the invention, reference has been made to preferred embodiments. However, those skilled in the timepiece art and familiar with this disclosure may recognize additions, deletions, substitutions or other modifications manent magnet means relative to said switch means to adust the magnetic arresting force acting on said switch means.

3. A timepiece according to claim 1 further including:

means operable to permit axial adjustment of said permanent magnet means relative to said generally potshaped field return means.

4. A timepiece according to claim 1 wherein said permanent magnet means comprises a platinum-cobalt alloy.

5. A timepiece according to claim 1 wherein said permanent magnet means is mounted peripherally adjacent a switch wheel and is operable to exert a magnetic, arresting influence on peripheral teeth of said switch wheel.

6. A timepiece according to claim 1 wherein:

said switch means comprises an armature fork;

said fork is disposed in driving engagement with a switch wheel;

said timepiece further including spaced stops operable to limitpivoting movement of said fork; and

said fork arrestingly cooperates with said magnet means at each extremity of pivoting movement of said fork.

7. A timepiece according to claim 1 wherein:

said switch means includes non-magnetic body means, and

ferromagnetic means coating at least a portion of said body means and operable to arrestingly cooperate with said magnet means.

8. A timepiece comprising:

switching means;

arresting means operable to periodically arrest movement of said switching means and includes magnet means, and

shroud means disposed generally peripherally adjacent said magnet means and extending generally between pole defining portions thereof; and

non-magnetic gap means interposed laterally between said magnet means and said shroud means at one pole defining end of said magnet means operable to face a portion of said switching means and arrest movement thereof; another pole defining end of said magnet means being disposed in generally contiguous relation with said shroud means.

l t i 

1. A device for effecting the magnetic arresting of switch means of a timepiece, said device comprising: magnet means operable to restrainingly act upon said switch means to stop said switch means between successive continuous switching movements thereof; said magnet means including bar-shaped permanent magnet means and generally pot-shaped field return means generally encircling said bar-shaped permanent magnet means.
 2. A timepiece according to claim 1 Further including: means operable to permit axial adjustment of said permanent magnet means relative to said switch means to adjust the magnetic arresting force acting on said switch means.
 3. A timepiece according to claim 1 further including: means operable to permit axial adjustment of said permanent magnet means relative to said generally pot-shaped field return means.
 4. A timepiece according to claim 1 wherein said permanent magnet means comprises a platinum-cobalt alloy.
 5. A timepiece according to claim 1 wherein said permanent magnet means is mounted peripherally adjacent a switch wheel and is operable to exert a magnetic, arresting influence on peripheral teeth of said switch wheel.
 6. A timepiece according to claim 1 wherein: said switch means comprises an armature fork; said fork is disposed in driving engagement with a switch wheel; said timepiece further including spaced stops operable to limit pivoting movement of said fork; and said fork arrestingly cooperates with said magnet means at each extremity of pivoting movement of said fork.
 7. A timepiece according to claim 1 wherein: said switch means includes non-magnetic body means, and ferromagnetic means coating at least a portion of said body means and operable to arrestingly cooperate with said magnet means.
 8. A timepiece comprising: switching means; arresting means operable to periodically arrest movement of said switching means and includes magnet means, and shroud means disposed generally peripherally adjacent said magnet means and extending generally between pole defining portions thereof; and non-magnetic gap means interposed laterally between said magnet means and said shroud means at one pole defining end of said magnet means operable to face a portion of said switching means and arrest movement thereof; another pole defining end of said magnet means being disposed in generally contiguous relation with said shroud means. 